1. Field of the Invention
The present invention relates to a quenchant, and in particular relates to a polymeric quenchant for adjusting cooling curve.
2. Description of the Related Art
Hardening of steel components is one of the most commonly practiced heat treatment operations in the steel industry. The hardening process comprises heating the steel components to austenitizing temperature (about 800-1000° C.), soaking the steel components at austenitizing temperature for thermal homogenization, and then quenching the steel components in an appropriate medium to room temperature. Quenching is a process whereby a steel component heated to a given elevated temperature is rapidly cooled by immersion in a quench bath containing compositions having a high heat-extracting capability such as air, water, brines, oils or polymer solutions.
Water and brine baths are easily disposed of and relatively inexpensive, however, such baths cool at extremely rapid rates and frequently provide metals quenched therein with a strained microstructure that is susceptible to warpage and cracking. Oil baths typically provide the quenched metals with relatively slow cooling rates, however, oils are expensive materials to use, have relatively low flash points which create a risk of fire, and oftentimes leave an undesirable film on the quenched metals.
Low cost aqueous solutions or dispersions of organic polymers have been developed which combine many of the cooling rate advantages of oils with the safety and disposal features of water and brine baths. Unlike oils which tend to form undesirable degradation products, which require removal from tanks prior to bath replacement, organic polymer-containing quench baths generally do not form system-fouling products. Thus, organic polymer-containing compositions are of particular interest for development.
However, quenching effect relates to quenchant cooling rate, specific heat, viscosity, and thermal conduction so that different quenchants are required for different types of steels. Thus, although the traditional polymer-containing quenchant simultaneously has the advantages of the water and oil quenchant solutions, it still does not satisfy steel industry requirements. Thus, a novel quenchant and quenching process are needed.